The present invention is concerned with an apparatus for adjusting the length of the sheath of a bowden cable guiding a cable tensioned between an actuating element and a gearing component to be driven and in particular it applies to the actuation cable for handbrakes of automobiles and similar vehicles.
Such devices are already known, for instance from West German patents 20 14 129 corresponding to U.S. Pat. No. 3,572,159 and 21 39 278 corresponding to U.S. Pat. No. 3,710,645 the disclosures of which are incorporated herein by reference. The devices described in these and other documents to automatically adjust the length of bowden cable sheaths all operate with gears meshing under spring pressure and upon an operationally determined shortening of the bowden cable sheath, they extend it by another spring mounted between a stationary seat and the sheath forcing this sheath further away from the seat, namely extending it, the meshing teeth slipping over each other.
However, devices of this kind are unsuited for bowden cables transmitting substantial forces. In order that satisfactory automatic adjustment be achieved with these known devices, the tooth-depth of the meshing teeth may not be excessive, just as the spring ensuring meshing must not be excessively strong. As a result, a bowden cable so equipped can only transmit minor forces, for instance the relatively small forces transmitted by a gas-pull in automobiles. Where larger forces are concerned, for instance such as must be transmitted by the hand or emergency brake in automobiles (on the average about 200 kg), the comparatively fine toothing cannot withstand the pressure: teeth become deformed, are squeezed etc. If on the other hand, the tooth-depth is made so large that the teeth withstand such high loads, then adjustment no longer is satisfactory.